[Jack-Devel] Fwd: jack 1.9.8 + many many connections = problems?

i accidentally replied only to stephane.

---------- Forwarded message ----------
From: Paul Davis <[hidden]>
Date: Tue, 3 Jan 2012 07:03:59 -0500
Subject: Re: [Jack-Devel] jack 1.9.8 + many many connections = problems?
To: Stéphane Letz <[hidden]>

On 1/3/12, Stéphane Letz <[hidden]> wrote:
>>> Le 2 janv. 2012 à 20:41, Fernando Lopez-Lezcano a écrit :
 I finally traced the problem to a few un-initialized
>> variables in a supercollider ugen (LR4 high pass and low pass filters used
>> in the speaker crossover). Those were the cause of the big noises in the
>> output stream. I still can't think how this could result in an audio port
>> that stops working! Must be something inside alsa itself?

we've seen this with plugins inside ardour that are able to
"accidentally" silence all output from the ardour and even other JACK
clients. the problem is rarely reproducable outside of the reporter's
machine, until it happens to someone else.

i suspect that its caused by a pointer walk that causes the plugin to
overwrite all/some of the shared memory segment in which port buffers
are held. if the plugin starts "early" enough in the memory segment,
but "late" enough in the timing schedule, it gets to effectively
silence whatever other clients did.

i don't know of a way to stop this sort of thing - it seems one of the
unfortunate downsides of (a) plugins and (b) a system like JACK in
which several processes share access to the memory in which they all
store (a specific kind of) data.

1325592288.14953_0.ltw:2,a <CAFa_cK=OffXtb_15aY45dHftETXpTxhpOf9cogshHPm65Gus8w at mail dot gmail dot com>